Phosphorus mining and bioavailability for plant acquisition: environmental sustainability perspectives

This review aims to examine microbial mechanisms for phosphorus (P) solubilization, assess the impacts of P mining and scarcity, and advocate for sustainable recycling strategies to enhance agricultural and environmental resilience. Phosphorus is an indispensable macronutrient for plant growth and agricultural productivity, yet its bioavailability in cultivation systems is often constrained. This scarcity has led to a heavy reliance on fertilizers derived from mined phosphate rock (PR), which is a finite resource usually contaminated with hazardous elements such as uranium, radium, and thorium. Plants absorb only about 10-20% of P from applied fertilizers, leading to significant inefficiencies and negative environmental consequences. Additionally, the uneven geographic distribution of PR reserves exacerbates global socioeconomic and geopolitical vulnerabilities. Healthy soils enriched with diverse microbial communities provide a sustainable avenue to address these growing challenges. Rhizospheric organisms, including phosphorus-solubilizing and phosphorus-mineralizing bacteria and arbuscular mycorrhizal fungi, are capable and pivotal in the sustainable conversion of inorganic and organic P into bioavailable forms, reducing reliance on synthetic fertilizers. The mechanisms used by these microbes often include releasing organic acids to lower soil pH and solubilize insoluble inorganic phosphorus compounds and the production of enzymes, such as phosphatases and phytases, to break down organic phosphorus compounds, including phytates, into bioavailable inorganic phosphate. Some microbes secrete chelating agents, such as siderophores, to bind metal ions and free phosphorus from insoluble complexes and use biofilms for P exchange. This review also advocates for the recycling second-generation P from organic waste as a sustainable and socially equitable alternative to conventional phosphate mining.